Consuming cow’s milk may aggravate multiple sclerosis (MS) symptoms in a subset of patients with an intolerance to bovine casein, according to a study published in the Proceedings of the National Academy of Sciences of the United States of America.

“Our data suggest that patients with antibodies to bovine casein might benefit from restricting dairy products from their diet,” researchers advised.

The suggestion of a link between cow’s milk consumption and MS prevalence has been around since the 1990s, researchers explained. To investigate the connection, they injected mice with various cow’s milk proteins and found when they administered casein along with an effect enhancer, the mice developed neurological disorders. Electron microscopy revealed damage to the myelin sheath surrounding nerve fibers.

“We suspected that the reason was a misdirected immune response, similar to that seen in MS patients,” said researcher Rittika Chunder, PhD, of the University of Bonn in Germany. “The body’s defenses actually attack the casein, but in the process they also destroy proteins involved in the formation of myelin.”

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When researchers looked at different molecules important for myelin production, they noticed a close resemblance between casein and myelin-associated glycoprotein (MAG). In the affected mice, antibodies to casein were also active against MAG, they found. In other words, the mice’s defenses against casein were also directed against MAG and, subsequently, destabilized the myelin. When researchers added casein antibodies from the mice to human brain tissue, they accumulated in cells responsible for myelin production.

According to the study, the response of B cells in the blood is particularly strong in patients with MS who have a casein allergy. When these patients consume fresh dairy products, the immune system produces loads of casein antibodies — and, because of cross-reactivity with MAG, the antibodies also damage the myelin sheath.

“We are currently developing a self-test with which affected individuals can check whether they carry corresponding antibodies,” said researcher Stefanie Kürten, MD, from the Institute of Anatomy at University Hospital Bonn. “At least this subgroup should refrain from consuming milk, yogurt, or cottage cheese.”

References

Chunder R, Weier A, Mäurer H, et al. Antibody cross-reactivity between casein and myelin-associated glycoprotein results in central nervous system demyelination. Proc Natl Acad Sci U S A. 2022;119(10):e2117034119. doi: 10.1073/pnas.2117034119

Milk may exacerbate MS symptoms. News release. University of Bonn. March 1, 2022. Accessed March 21, 2022.